Non-volatile semiconductor memories are gaining increasing importance in the field of multimedia and other applications. For example, non-volatile memories are nowadays used in a broad variety of electronic devices such as cellular telephones, digital cameras, personal digital assistants, mobile computing devices, non-mobile computing devices and many other electronic devices.
For example, non-volatile memories may utilize a floating gate as charge storage region that is positioned above and insulated from a channel region in a semiconductor substrate. A control gate is provided over and insulated from the floating gate. The floating gate can store charges and can therefore be programmed/erased between different states, e.g., binary “1” and binary “0.” Recently, multi-level non-volatile memory cells also have been developed.
Moreover, non-volatile memories may also be based upon charge trapping technology. As charge trapping stacks for example, SONOS (silicon-oxide-nitride-oxide-silicon) and TANOS (tantal nitride-aluminum oxide-nitride-oxide-silicon) stacks may be used. In these stacks, the silicon nitride layer serves as charge storage layer.
In so-called NAND flash memories, NAND strings of non-volatile memory cells are connected in series. The ends of such NAND strings are connected to a common bit line and a common source-line by respective select transistors.
With increasing integration smaller than 45 nm, it becomes an increasingly challenging task to avoid capacitive coupling between neighboring floating gates which might influence neighboring memory cells.